ESO | NAOJ | NRAO | ALMA | 2016 Jun 08
An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has witnessed a cosmic weather event that has never been seen before — a cluster of towering intergalactic gas clouds raining in on the supermassive black hole at the centre of a huge galaxy one billion light-years from Earth. The results will appear in the journal Nature on 9 June 2016.
- Composite image of Abell 2597 Brightest Cluster Galaxy. The background image (blue) is from the Hubble Space Telescope. The foreground (red) is ALMA data showing the distribution of carbon monoxide gas in and around the galaxy. The pull-out box is the ALMA data of the 'shadow' (black) produced by absorption of the millimeter-wavelength light emitted by electrons whizzing around powerful magnetic fields generated by the galaxy's supermassive black hole. The shadow indicates that cold clouds of molecular gas are raining in on the black hole. Credit: B. Saxton (NRAO/AUI/NSF); G. Tremblay et al.; NASA/ESA Hubble; ALMA (ESO/NAOJ/NRAO)
The new ALMA observation is the first direct evidence that cold dense clouds can coalesce out of hot intergalactic gas and plunge into the heart of a galaxy to feed its central supermassive black hole. It also reshapes astronomers’ views on how supermassive black holes feed, in a process known as accretion.
Previously, astronomers believed that, in the largest galaxies, supermassive black holes fed on a slow and steady diet of hot ionised gas from the galaxy’s halo. The new ALMA observations show that, when the intergalactic weather conditions are right, black holes can also gorge on a clumpy, chaotic downpour of giant clouds of very cold molecular gas. ...
Near the centre of this galaxy the researchers discovered just this scenario: three massive clumps of cold gas are careening toward the supermassive black hole in the galaxy’s core at about a million kilometres per hour. Each cloud contains as much material as a million Suns and is tens of light-years across.
Normally, objects on that scale would be difficult to distinguish at these cosmic distances, even with ALMA’s amazing resolution. They were revealed, however, by the billion-light-year-long “shadows” they cast toward Earth. ...
Cold, clumpy accretion onto an active supermassive black hole - Grant R. Tremblay et al